Dermal bone: Difference between revisions

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(Tried to rewrite in proper English.)
{{Unreferenced|date=December 2009}}
A '''dermal bone''' (or '''membrane bone)-''' is a bony structuresstructure derived from [[intramembranous ossification]] that formforming components of the [[vertebrate]] [[skeleton]] including the [[skull]], jaws[[jaw]]s, gills[[gill]]s, fins[[fin]]s and [[exoskeleton]] (of [[tortoise]]s and [[turtle]]s). In contrast to [[endochondral ossification|endochondral]] bone, dermal bone does not form from cartilage first andthat then calcifycalcifies. Dermal bone is formed within the [[dermis]] and it grows by accretion only; that is, the outer portion of the bone is deposited by [[osteocyte]]s.
The function of some dermal bone is conserved throughout vertebrates, varyingalthough there is variation in shape and numbersin the number of bones in the [[skull roof]] and postcranial structures. In [[bony fish]], dermal bone is found throughoutin the bodyfin in[[Ray the(fish fin anatomy)|rays]] and scales. Special examples of dermal bones include the [[clavicle]], [[patella]], and ''[[os cordis]]''.